1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device. More particularly, the present invention relates to an array substrate, a manufacturing method of the same and a fabricating method of a liquid crystal display device including the array substrate.
2. Discussion of the Related Art
Liquid crystal display (LCD) devices use the optical anisotropy and polarization properties of liquid crystal molecules to produce an image. Liquid crystal molecules have a definite alignment as a result of their long, thin shapes and are arranged to have initial pretilt angles. The alignment direction can be controlled by applying an electric field. Specifically, variations in an applied electric field influence the alignment of the liquid crystal molecules. Due to the optical anisotropy, the refraction of incident light depends on the alignment direction of the liquid crystal molecules. Thus, by properly controlling the applied electric field, an image that has a desired brightness can be produced.
A manufacturing process of the LCD devices includes a thin film transistor array process for forming a lower substrate, an upper substrate forming process, and a liquid crystal cell process. During the thin film transistor array process, a plurality of gate and data lines are formed on a substrate, and plurality of thin film transistors are formed at crossing portions of the gate and data lines. Then, a pixel electrode is formed in a pixel region of the lower substrate. During the upper substrate forming process, a color filter, a black matrix, and a common electrode are sequentially formed on a substrate. The liquid crystal cell process includes an alignment layer forming process, a rubbing process, a cleaning process subsequent to the rubbing process, an attachment process of the upper and lower substrates, and a liquid crystal material injection process. The aforementioned liquid crystal cell process will be described in greater detail hereinafter with reference to attached drawings.
FIG. 1 shows a flow chart of a manufacturing process of an LCD device according to the related art.
Step ST1 includes the preparation of a first substrate, which has a thin film transistor and a pixel electrode, and a second substrate, which has a black matrix, a color filter layer and a common electrode.
Step ST2 includes the tests of the first and second substrates. Gate and data lines are inspected through testing of the first substrate. The test of the first substrate may be referred to as an in-process test multi-pattern search (IPT-MPS). Test signals are provided to the gate and data lines through shorting bars that are formed on the first substrate. The shorting bars also prevent static electricity on the first substrate during the thin film transistor array process. Fine patterns of the color filter layer are inspected through testing of the second substrate.
Step ST3 includes the formation of first and second alignment layers on the pixel electrode and the common electrode, respectively. Step ST3 also includes coating a thin polymer film and rubbing the thin polymer film. The thin polymer film may be commonly referred to as an alignment layer. The thin polymer film must be uniformly formed, and the rubbing process must also be performed uniformly on the thin polymer film. The initial orientation of liquid crystal molecules is determined by the rubbing. The liquid crystal molecules normally display a uniform picture due to the rubbing of the alignment layer. Polyimide is widely used as a material of the thin polymer film.
During step ST4, a seal pattern is formed on either the first substrate or the second substrate, and spacers are sprayed on one of the first and second substrates to maintain a precise and uniform gap between the first and second substrates. The formation of the seal pattern includes forming a cell gap to allow for injection of liquid crystal material between the substrates. In addition, the seal pattern prevents the injected liquid crystal material from leaking outside the seal pattern. The seal pattern is commonly fabricated using a screen-printing method or a dispensing method of a mixing sealant formed from thermosetting resin and glass fiber. The spacer spray method can be divided into two different types: a wet spray method that involves spraying a mixture of alcohol and spacer material and a dry spray method that involves spraying spacer material alone.
Here, the seal pattern and the spacers are formed on different substrates. For example, the seal pattern may be formed on the second substrate, which has a relatively even surface, and the spacers may be formed on the first substrate, which functions as a lower substrate of the liquid crystal display device.
During step ST5, the first and second substrates are aligned and then are attached to each other along the seal pattern. The alignment accuracy of the substrates is decided by a margin and an alignment accuracy of several micrometers is required because light leakage occurs if the substrates are misaligned beyond the margin.
During step ST6, the attached substrates are divided into unit cells. The cell cutting process includes a scribing process that forms cutting lines on a surface of the substrate using a diamond pen or a cutting wheel of tungsten carbide, the hardness of which is higher than the hardness of the glass substrate. A breaking process divides the unit cells by using force. In this step, the shorting bars may be removed.
During step ST7, a liquid crystal material is injected between two substrates of the unit cells. Each unit cell has an area of several square centimeters and a gap of several micrometers. A vacuum injection method using the pressure difference between the inside and outside of the unit cells is commonly used as an effective injection method.
After finishing the liquid crystal material injection, the injection hole is sealed to prevent leakage of the liquid crystal material. Generally, an ultra violet (UV) curable resin is injected into the injection hole by use of a dispenser, and ultra violet light is then irradiated onto the resin to thereby harden the resin and seal the injection hole.
Alternatively, the liquid crystal material may be dropped on one of the first and second substrates and then the first and second substrates may be attached.
During step ST8, each unit cell is inspected through an autoprobe test. Line defects and point defects are detected through the autoprobe test. Signals are provided to gate pads and data pads on the first substrate, and an LC panel is practically driven.
FIG. 2 is a schematic plan view of an array substrate for an LCD device according to the related art.
In FIG. 2, an active area AA and a pad area PA are defined on a substrate 1. Gate lines GL and data lines DL are formed in the active area AA, and gate pads GP and data pads DP are formed in the pad area PA. First, second, third and fourth shorting bars 2, 4, 6 and 8 are also formed in the pad area PA. The first and second shorting bars 2 and 4 are connected to the gate pads GP, and the third and fourth shorting bars 6 and 8 are connected to the data pads DP. The first shorting bar 2 is connected to even gate lines GL through the gate pads GP, and the second shorting bar 4 is connected to odd gate lines GL through the gate pads GP. The third shorting bar 6 is odd data lines DL through the data pads DP, and the fourth shorting bar 8 is even data lines DL through the data pads DP.
The first, second, third and fourth shorting bars 2, 4, 6 and 8 are used to test the array substrate at the step ST2 of FIG. 1 and are cut at the step ST6 of FIG. 1. Then, the autoprobe test is performed. To apply the signals to the gate pads GP and the data pads DP, a needle frame is used, and thus line defects, point defects or contamination spots are detected.
FIG. 3 is a view schematically illustrating a needle frame according to the related art.
In FIG. 3, the needle frame 25 includes a body 28 and contact portions 30. The contact portions 30 have a pin shape and are formed of a conductive metallic material such as nickel (Ni). The contact portions 30 contact the gate pads GP and the data pads DP of FIG. 2 and provide test signals to the gate pads GP and the data pads DP.
However, because the contact portions 30 correspond to respective gate pads GP and respective data pads DP, the number of the contact portions 30 should increase according as the resolution of an LCD device becomes high. Therefore, manufacturing costs are increased.
Additionally, positions or distances of the gate pads GP and the data pads are varied according to the resolutions of the LCD device. Thus, various needle frames are required, and needle frames are changed according to the resolutions of the LCD device to thereby lower the productivity.